class Solution {//leetcode200——岛屿数量
private:
    int dx[4] = {0, 0, -1, 1};
    int dy[4] = {1, -1, 0, 0};
    void bfs(vector<vector<char>>& grid, int i, int j) {
        priority_queue<pair<int, int>> que;
        que.push({i, j});
        vis[i][j] = true;
        while (que.size()) {
            auto [a, b] = que.top();
            que.pop();
            for (int k = 0; k < 4; k++) {
                int x = a + dx[k];
                int y = b + dy[k];
                if (x >= 0 && x < m && y >= 0 && y < n && !vis[x][y] &&grid[x][y] == '1') {
                    que.push({x, y});
                    vis[x][y]=true;
                }
            }
        }
    }

public:
    int numIslands(vector<vector<char>>& grid) {
        m = grid.size();
        n = grid[0].size();
        vis.resize(m, vector<bool>(n, false));
        for (int i = 0; i < m; i++) {
            for (int j = 0; j < n; j++) {
                if (grid[i][j] == '1' && vis[i][j] == false) {
                    bfs(grid, i, j);
                    ret++;
                }
            }
        }
        return ret;
    }

private:
    int ret = 0;
    int m;
    int n;
    vector<vector<bool>> vis;
};